Printed circuit boards (PCBs) are generally mounted in frames, with a large number of PCBs mounted in each frame, with as high a density as possible, in order to save space. A typical PCB comprises a pattern of electrical interconnections on a flat rectangular sheet of insulating material (such as glass-fibre reinforced resin) and carries a number of components on one of its flat faces. The four edges of the PCB can be referred to as a front edge, a back (or rear) edge, a top edge, and a bottom edge. The PCB slides into guide channels in the frame, the PCBs lying normally in a vertical plane with the top edge in a top guide channel, the bottom edge in a bottom guide channel, and the rear edge carrying a set of connections which mate with a corresponding set of connections mounted to the frame. The front edge of the PCB may carry two devices (one usually near the top, and one usually near the bottom) to aid in inserting, removing or retaining the PCB relative to the frame.
Various prior art devices for performing this function are depicted in the following U.S. patents and attention is directed to them: U.S. Pat. No. 4,064,551 dated Dec. 20, 1977 to R. Lightfoot; U.S. Pat. No. 3,798,507 dated Mar. 19, 1974 to N. F. Damon and H. G. Yeo; U.S. Pat. No. 3,952,232 dated Apr. 20, 1976 to R. A. Coules; and U.S. Defensive Publication T876,004 dated July 28, 1970 to J. Andreini et al. Another prior art device in pictured on pages 78 and 79 of the Fall 1975 Issue of Telesis published by Bell-Northern Research Ltd., Ottawa, Ontario, Canada.
The prior art device on pages 78 and 79 of the Telesis article, previously mentioned, is referred to as a latching lever. This prior art latching lever will be described in greater detail later, but its latching feature will now be briefly described. The latching feature is accomplished by a hooked portion that straddles the PCB and engages a pin mounted in the PCB. A handle, attached to the hooked portion, enables the hooked portion to be disengaged from the pin, thereby allowing the latching lever to pivot. The handle and hooked portion form one integral unit which is attached to the main body portion of the latching lever by a thin web of material. This thin web of material permits the latching lever to latch and to unlatch, but it is also a weak point in the latching lever in that the line of force, between the handle and the lever's pivot point, for pivoting the lever, is carried by the web. This results in a lot of stress being applied to the web making it prone to breakage.
The present invention overcomes this problem by providing a latching lever with an improved latching mechanism. The latching mechanism of the latching lever of the present invention comprises a hooked portion flexibly connected to the body portion of the latching lever, an actuating member solidly connected to the hooked portion for moving the hooked portion relative to the body portion, and a stop portion, solidly connected to the body portion for limiting the movement of the actuating member. The line of force, between the handle and the lever's pivot point, for pivoting the lever, is carried by the stop portion and the body portion; it does not pass through the material by which the hooked portion is mounted to the body portion.
Stated in other terms, the present invention is a latching lever for use with an object for aiding the entry of the object into a mating apparatus, for securing the object in the mating apparatus, and for aiding the removal of the object from the mating apparatus, the latching lever characterized by: a body portion for pivotal connection to the object, about a pivot point; a hooked portion, flexibly mounted to the body portion, and projecting therefrom at the end of the body portion remote from the pivot point, for engaging a projection attached to the object; an actuating member, solidly connected to said hooked portion and protruding therefrom, for moving the hooked portion relative to the body portion, so as to selectively disengage the hooked portion from the projection; a stop portion, solidly connected to the body portion and protruding therefrom, located adjacent the actuating member, but spaced therefrom so as to provide a limit to the movement of the actuating member.
Stated in yet other terms, the present invention is a latching lever for use with a piece of sheet material for aiding the entry of the piece into a mating apparatus, for securing the piece in the mating apparatus, and for aiding the removal of the piece from the mating apparatus, the latching lever characterized by: a body portion for pivotal connection to the object, about a pivot point; a hooked portion, flexibly mounted to the body portion, and projecting therefrom at the end of the body portion remote from the pivot point, for engaging a projection attached to the piece; an actuating member, solidly connected to the hooked portion and protruding therefrom, for moving the hooked portion relative to the body portion, so as to selectively disengage the hooked portion from the projection; a stop portion, solidly connected to the body portion and protruding therefrom, located adjacent the actuating member, but spaced therefrom so as to provide a limit to the movement of the actuating member; an arm portion protruding from the body portion, close to the pivot point, for engaging the mating apparatus during entry thereinto, for aiding the entry, and for blocking the removal of the piece until the lever is pivoted to an alternate position.
Stated in still other terms, the present invention is the combination of a printed circuit board (PCB) and a latching lever for use in aiding the entry of the PCB into a mating apparatus, for securing the PCB in the mating apparatus, and for aiding the removal of the PCB from the mating apparatus, the combination characterized by: a printed circuit board; at least one latching lever pivotally connected to the printed circuit board; at least one stud attached to the PCB, and protruding from both planar surfaces of the PCB, for engaging the lever, one stud for each lever; the latching lever comprising: a body portion for pivotal connection to the PCB, about a pivot point; a hooked portion, flexibly mounted to the body portion, and projecting therefrom at the end of the body portion remote from the pivot point, for selectively engaging the stud; an actuating member, solidly connected to the hooked portion and protruding therefrom, for moving the hooked portion relative to the body portion, so as to selectively disengage the hooked portion from the stud; a first stop portion, solidly connected to the body portion and protruding therefrom, located adjacent the actuating member, but spaced therefrom so as to provide a limit to the movement of the actuating member; a second stop portion, solidly connected to said body portion and protruding therefrom, located adjacent said hooked portion, but spaced therefrom so as to provide a limit to the movement of said hooked portion; an arm portion protruding from the body portion, close to the pivot point, for engaging the mating apparatus during entry thereinto, for aiding the entry, and for blocking the removal of the piece until the lever is pivoted to an alternate position.